1. Field of the Invention
The present disclosure relates to a fuel cell.
2. Discussion of the Background
For example, a solid polymer electrolyte fuel cell includes a power generation cell (unit cell) including a membrane electrode assembly (MEA) and separators sandwiching the MEA therebetween. The MEA includes a solid polymer electrolyte membrane, which is made from a polymer ion-exchange membrane, and an anode electrode and a cathode electrode sandwiching the solid polymer electrolyte membrane therebetween. A fuel cell in which several tens or hundreds of such power generation cells are stacked is used, for example, as a vehicle mounted fuel cell stack.
A fuel cell typically includes a so-called internal manifold for supplying a fuel gas and an oxidant gas, which are reactant gases, respectively to the anode electrode and to the cathode electrode of each of power generation cells that are stacked.
An internal manifold includes reactant gas inlet manifolds (a fuel gas inlet manifold and an oxidant gas inlet manifold) and reactant gas outlet manifolds (a fuel gas outlet manifold and an oxidant gas outlet manifold), which extend in a stacking direction in which the power generation cells are stacked. Each reactant gas inlet manifold is connected to the inlet side of a corresponding one of reactant gas channels (a fuel gas channel or an oxidant gas channel), through which a reactant gas is supplied along an electrode surface. Each reactant gas outlet manifold is connected to the outlet side of a corresponding one of the reactant gas channels.
In this case, the width of the opening of the reactant gas inlet manifold and the width of the opening of the reactant gas outlet manifold are set considerably smaller than the width of the reactant gas channel. Therefore, in order to make the reactant gas flow uniformly and smoothly through the reactant gas channel, it is necessary to provide a buffer portion in the vicinity of each of the reactant gas inlet manifold and the reactant gas outlet manifold.
For example, Japanese Unexamined Patent Application Publication No. 2010-282868 discloses a fuel cell illustrated in FIG. 17, in which an oxidant gas channel 3 is formed on a surface 1a of a cathode-side metal separator 1 so as to be connected to an oxidant gas inlet manifold 2a and an oxidant gas outlet manifold 2b. On a surface 1b of the cathode-side metal separator 1, a coolant channel 4 is formed on the back side of the oxidant gas channel 3.
Linear guide protrusions 7a and 7b and embossed portions 8a and 8b are formed on the cathode-side metal separator 1. The linear guide protrusions 7a and 7b protrude from medium height portions 5a and 5b toward the oxidant gas channel 3 and form connection guide channels 6a and 6b. The embossed portions 8a and 8b protrude from the medium height portions 5a and 5b toward the coolant channel 4 and form embossed channels.
With such a structure, water generated on the oxidant gas channel 3 side can be smoothly discharged using the cathode-side metal separator 1 having a wave-like shape, and a coolant can smoothly flow through the coolant channel 4.